The present invention relates to a voltage sensing circuit in which a reference voltage generating circuit is operative to produce a reference voltage whose value is determined as a function of absolute temperature, with the reference voltage level being made independent of the individual characteristics of elements in the reference voltage generating circuit.
It is necessary to provide an accurately defined reference voltage, in a voltage sensing circuit, so as to provide a reference by which the voltage level to be sensed can be compared. It is necessary, therefore, that the reference voltage level either be predetermined by suitable circuit design, or that adjustment means such as external adjustment terminals be provided. In the prior art, elements such as Zener diodes have been utilized to produce a reference voltage in voltage sensing circuits, so that the degree of accuracy of the reference voltage is determined by the individual characteristics of such an element. Thus, due to manufacturing variations, it is difficult to achieve a high degree of accuracy in the reference voltage level, without selection of particular elements or providing external adjustment means.
There is therefore a requirement for a voltage sensing circuit having a reference voltage generating circuit which produces an accurately defined reference voltage whose level will be substantially independent of variations in element characteristics, so that element selection or external adjustment of the reference voltage level is unnecessary. These requirements are especially important for a voltage sensing circuit which is to be formed within an integrated circuit chip, and are met by a voltage sensing circuit according to the present invention as described herein.